1. Field of the Invention
The present invention relates to an external electronic control type electrodeless lamp and, more particularly, to an electrodeless lamp that utilizes magnetic core to create a magnetic field, and current generated due to change in the magnetic field is supplied to conductive plates for lighting purposes.
2. Description of the Related Art
Lighting instruments are a necessity in daily life. Fluorescent lamps, mercury lamps, and current electronic energy-saving lamps have been provided to meet different stable illumination needs through various designs for the purposes of best illumination effects. Electrodeless lamps utilizing electromagnetic induction effect have been developed and include a magnetic core in a lighting device (i.e., a lighting body such as a lamp, lamp shade, electroluminescent lamp, or bulb, or an interface for light source output) to create induction current. Electrodeless lamps are named for not utilizing electrodes to convert external energy into energy required for operation inside the lighting device. Such electrodeless lamps create alternating magnetic field that generates induction current in the lighting device, which results in discharge of the vapor mixture of low-pressure mercury and inert gas, and visible light can be seen through conversion by fluorescent powders. Since less heat is generated, the electrodeless lamps are durable and, thus, popular.
However, the lighting device of the conventional electrodeless lamps is limited in size and shape, for the magnetic core is mounted in the lighting device. Miniaturization of the lighting device is limited. Applicant's Taiwan Patent Application No TW 94219444 filed on Nov. 10, 2005 discloses an external electronic control type electrodeless lamp including a lighting device that has at least a first conductive plate and a second conductive plate each of which is electrically connected to an external electronic control system in which a magnetic core is mounted. The magnetic core, when energized, creates a magnetic field, and current generated due to change in the magnetic field is supplied to the conductive plates, thereby lighting the lighting device.
However, it was found that distribution of the magnetic lines of force of the first and second conductive plates in the lighting device is in pairs or in the same direction. There is, therefore, a need for improvement in the distribution of the magnetic line of force.